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Old 14-02-2012, 12:09   #16
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Re: Epoxy Sheath for an Old Wooden Sailboat

That's interesting. When I look at boats for sale in New Zealand (which I do often; long story) I see many that are described as "glass over ply" or "glass over Kauri."

Consensus here is that those would be a bad choice? Or is the issue different if the boat is designed and built that way?

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Some instances:

DAVIDSON CUSTOM 1974 For Sale in Auckland

WRIGHT 9.21 1988 For Sale in Auckland
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Old 14-02-2012, 12:12   #17
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Re: Epoxy Sheath for an Old Wooden Sailboat

The biggest problem with glassing over a wood hull is that freshwater can get in the boat through any number areas where bedding has failed or an open port or hatch and once it has gotten aboard it gets between the glass and the wood. Moisture sits there and causes dry rot. It might take a few years but that marks the end of the boat.
Good luck on whatever you do decide to do but I've seen a lot of problems with boats that have sheathing.
kind regards,
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Old 14-02-2012, 12:38   #18
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Glass over ply is fairly common especially in trimaran designs. Not having built with this or owned a boat like this I can't speak on their durability. They do seem to be a favourite material combination of home builders as well. These two materials have similar mechanical properties and stress strain curves so would be compatible. A sheet of ply if you push in the middle deforms, if you try to deform it along the sheer, ie make s flat square piece of ply into a rhomboid it would not budge, this would hold true for a similar sized piece of epoxy/polyester resigned sheet of fiberglass.

Real wood, unidirectional grain versus multi directional ply, does not share these same properties. Additionally carvel planked hulls specifically take advantage of the unidirectional aspect of wood to allow the boat to flex where she should and be incompressible where she shouldn't.

Long story short, I have no idea if a glassed over plywood boat is any good...

...but the materials make sense and if the boat was built and designed to be glassed then it probably is a sound boat.
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Old 14-02-2012, 13:40   #19
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Re: Epoxy Sheath for an Old Wooden Sailboat

Glass over ply is much different than glass over planking. The Newporter 40 used full length (I think) custom made sheets of ply for each chine. The glass was built up over the hull deck and cabin fairly thick. Many of those boats are in service today. But like it was pointed out by other posters here. glass over planking is a recipes for disaster.
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Old 14-02-2012, 13:54   #20
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Re: Epoxy Sheath for an Old Wooden Sailboat

A quick fix to fix what? Commercial vessels are of steel (mostly).
C-flex was/is developed for repair of wooden boats following the same procedure as with other fibreglass products. Whatever you wis, you have to bond it and to bond it you do with a resin, be it polyester or epoxy.

It is for the quicly building of small boats or repair as FSMike writes correctly but it would lead to the sam effect as other methods already mentioned here.
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Old 14-02-2012, 21:22   #21
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Re: Epoxy Sheath for an Old Wooden Sailboat

Quote:
Originally Posted by MacG View Post
A quick fix to fix what? Commercial vessels are of steel (mostly).
---
Wooden fishing boats, such as shrimp trawlers, etc.
I recommend anybody interested in the exact methodology visit the web site sintesfiberglass, then click on c-flex.
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Old 15-02-2012, 03:03   #22
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Re: Epoxy Sheath for an Old Wooden Sailboat

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Originally Posted by Honey Ryder View Post
i am looking at options to improve the watertightness of an old wooden hull, especially under the stresses imposed by the rig in decent winds.

i have found that if it is blowing hardish then she leaks and pumping out is annoying.

a reputable boatyard suggested removing all the old fashioned caulking and filling with epoxy. am not too sure how that would work as the wood expands and contracts with temperature, etc.

so i was wondering about laying an epoxy/fibreglass skin over the whole hull.

does anybody have any experience doing this?
Yes i have but not a sail boat. No i would not do it to an old boat that i valued unless it was to extend its life by a few years without paying others. Much i what i have written will repeat what others have said.


Both boats were over 50 years old and built out of Australian timbers. One was a 26 foot estuary/inshore fishing boat which i need to be able to leave unattended including up rivers for as long as a week at at time. The boat did leak a little, need the caulking redoing and had some planks that should have been replaced. The "upgrades" to the boat included glassing in the self draining deck so it was not that much of an extension just to skin the hull while i was at it. By the time that the boat had dried enough to do the glass work all the planks had shrunk and some of them were coming loss from the ribs and stringers. While most of the moisture left the boat the salt had not and when in was reintroduced to a marine environment the timbers slowly swelled again. The other issues was trying to get a good adherence to the timber. Remember some of the treatments that have been used in the not so distant past. One of these was read lead mixed with linseed oil, lovely to fully remove and better not to have in your lungs. Between dry rot(existing spores and lack of ventilation and penetration of rain water) and unseen cobra infestation the boat was dead in about 5 years.


The other old boat was a 17 foot rowing dingy with similar issues. The out side of the boat was cleared of paint (mainly by scraping with broken pains of glass, cheap ba$tard that i am) then dried out. I glassed the outside with 4 oz glass and gelcoat. As the boat was open and the timber already very degraded within a year the ribs and stringers were falling out. When i pulled the timber from the inside of the boat (less than 2 hours work and no fractures in the FG) there was no appreciable loss of stiffness, in part due to the penetration of the resign in to the gaps between the planks. I sanded the paint off the outside, added two layers of glass. When the keel was dug out i replaced it with sandwich layers of mat and 3 ply with plenty of resin. The glass ribs created by shrunken planks were then ground off. 3/4 inch marine ply was glued inside the transom, the 2 seats were replaced and a number of tea tree root knees were added at the points to make the boat more ridged. The inside of the boat was then completely glassed. Dam the is the one boat that i have owned that i really regret getting rid of so please excuse the thread drift.


I also built a couple of ply on spotted gum framed punts that were glassed inside and out but that is a very different situation because of penetration of resign into the outside layers of ply and good adhesion to virgin wood.
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Old 15-02-2012, 09:15   #23
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Re: Epoxy Sheath for an Old Wooden Sailboat

[QUOTE=MacG;887244] ---
C-flex was/is developed for repair of wooden boats following the same procedure as with other fibreglass products. Whatever you wis, you have to bond it and to bond it you do with a resin, be it polyester or epoxy.

---- QUOTE]

Actually, c-flex is bonded to the wood hull by applying the c-flex material over a layer of an elastomeric material, such as 5200, then stapling it with bronze staples through the material and over the fiberglass rods. No resin is used in this bonding process. Resin is applied after this process is complete.
I recommend the sintesfiberglass web site for further information.
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Old 15-02-2012, 10:01   #24
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Re: Epoxy Sheath for an Old Wooden Sailboat

Quote:
Originally Posted by Honey Ryder View Post
i am looking at options to improve the watertightness of an old wooden hull, especially under the stresses imposed by the rig in decent winds.

i have found that if it is blowing hardish then she leaks and pumping out is annoying.

a reputable boatyard suggested removing all the old fashioned caulking and filling with epoxy. am not too sure how that would work as the wood expands and contracts with temperature, etc.

so i was wondering about laying an epoxy/fibreglass skin over the whole hull.

does anybody have any experience doing this?
Not only no but HELL NO!

The only way I've seen to sheath a wooden boat (carvel in particular) is what was done on Oh Joy, my Knutson 35 yawl. C-FLEX applied into troweled on 3M 5200, rolled into it hard with a roller, stapled with Monel staples and wetted out in place. Afterwards, the boat MUST be protected from freshwater incursion from above or it will rot away.

BTW, to show how tough this stuff is, it took me four hours and five multitool blades to cut and peel away a 2" by 24" piece of the glass to fasten a rib. After that, I'll be fastening any replacements from the inside. It makes for an incredibly tough and stiff hull, without the issues found with most glass hulls while preserving the quiet of a wood hull. Ya absolutely have to stay on top of maintenance though or it will come back to bite ya.
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